2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
45 #include "ucioption.h"
51 //// Local definitions
57 enum NodeType { NonPV, PV };
59 // Set to true to force running with one thread.
60 // Used for debugging SMP code.
61 const bool FakeSplit = false;
63 // Fast lookup table of sliding pieces indexed by Piece
64 const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
65 inline bool piece_is_slider(Piece p) { return Slidings[p]; }
67 // ThreadsManager class is used to handle all the threads related stuff in search,
68 // init, starting, parking and, the most important, launching a slave thread at a
69 // split point are what this class does. All the access to shared thread data is
70 // done through this class, so that we avoid using global variables instead.
72 class ThreadsManager {
73 /* As long as the single ThreadsManager object is defined as a global we don't
74 need to explicitly initialize to zero its data members because variables with
75 static storage duration are automatically set to zero before enter main()
81 int min_split_depth() const { return minimumSplitDepth; }
82 int active_threads() const { return activeThreads; }
83 void set_active_threads(int cnt) { activeThreads = cnt; }
85 void read_uci_options();
86 bool available_thread_exists(int master) const;
87 bool thread_is_available(int slave, int master) const;
88 bool cutoff_at_splitpoint(int threadID) const;
89 void wake_sleeping_thread(int threadID);
90 void idle_loop(int threadID, SplitPoint* sp);
93 void split(Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
94 Depth depth, Move threatMove, bool mateThreat, int moveCount, MovePicker* mp, bool pvNode);
97 Depth minimumSplitDepth;
98 int maxThreadsPerSplitPoint;
99 bool useSleepingThreads;
101 volatile bool allThreadsShouldExit;
102 Thread threads[MAX_THREADS];
103 Lock mpLock, sleepLock[MAX_THREADS];
104 WaitCondition sleepCond[MAX_THREADS];
108 // RootMove struct is used for moves at the root at the tree. For each root
109 // move, we store two scores, a node count, and a PV (really a refutation
110 // in the case of moves which fail low). Value pv_score is normally set at
111 // -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed
112 // according to the order in which moves are returned by MovePicker.
117 RootMove(const RootMove& rm) { *this = rm; }
118 RootMove& operator=(const RootMove& rm);
120 // RootMove::operator<() is the comparison function used when
121 // sorting the moves. A move m1 is considered to be better
122 // than a move m2 if it has an higher pv_score, or if it has
123 // equal pv_score but m1 has the higher non_pv_score. In this
124 // way we are guaranteed that PV moves are always sorted as first.
125 bool operator<(const RootMove& m) const {
126 return pv_score != m.pv_score ? pv_score < m.pv_score
127 : non_pv_score < m.non_pv_score;
130 void extract_pv_from_tt(Position& pos);
131 void insert_pv_in_tt(Position& pos);
132 std::string pv_info_to_uci(const Position& pos, Value alpha, Value beta, int pvLine = 0);
137 Move pv[PLY_MAX_PLUS_2];
141 // RootMoveList struct is essentially a std::vector<> of RootMove objects,
142 // with an handful of methods above the standard ones.
144 struct RootMoveList : public std::vector<RootMove> {
146 typedef std::vector<RootMove> Base;
148 RootMoveList(Position& pos, Move searchMoves[]);
149 void set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss);
151 void sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
152 void sort_multipv(int n) { insertion_sort<RootMove, Base::iterator>(begin(), begin() + n); }
156 // When formatting a move for std::cout we must know if we are in Chess960
157 // or not. To keep using the handy operator<<() on the move the trick is to
158 // embed this flag in the stream itself. Function-like named enum set960 is
159 // used as a custom manipulator and the stream internal general-purpose array,
160 // accessed through ios_base::iword(), is used to pass the flag to the move's
161 // operator<<() that will use it to properly format castling moves.
164 std::ostream& operator<< (std::ostream& os, const set960& f) {
166 os.iword(0) = int(f);
171 // Overload operator << for moves to make it easier to print moves in
172 // coordinate notation compatible with UCI protocol.
174 std::ostream& operator<<(std::ostream& os, Move m);
181 // Maximum depth for razoring
182 const Depth RazorDepth = 4 * ONE_PLY;
184 // Dynamic razoring margin based on depth
185 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
187 // Maximum depth for use of dynamic threat detection when null move fails low
188 const Depth ThreatDepth = 5 * ONE_PLY;
190 // Step 9. Internal iterative deepening
192 // Minimum depth for use of internal iterative deepening
193 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
195 // At Non-PV nodes we do an internal iterative deepening search
196 // when the static evaluation is bigger then beta - IIDMargin.
197 const Value IIDMargin = Value(0x100);
199 // Step 11. Decide the new search depth
201 // Extensions. Configurable UCI options
202 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
203 Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
204 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
206 // Minimum depth for use of singular extension
207 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
209 // If the TT move is at least SingularExtensionMargin better then the
210 // remaining ones we will extend it.
211 const Value SingularExtensionMargin = Value(0x20);
213 // Step 12. Futility pruning
215 // Futility margin for quiescence search
216 const Value FutilityMarginQS = Value(0x80);
218 // Futility lookup tables (initialized at startup) and their getter functions
219 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
220 int FutilityMoveCountArray[32]; // [depth]
222 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
223 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
225 // Step 14. Reduced search
227 // Reduction lookup tables (initialized at startup) and their getter functions
228 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
230 template <NodeType PV>
231 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
233 // Common adjustments
235 // Search depth at iteration 1
236 const Depth InitialDepth = ONE_PLY;
238 // Easy move margin. An easy move candidate must be at least this much
239 // better than the second best move.
240 const Value EasyMoveMargin = Value(0x200);
243 /// Namespace variables
251 // Scores and number of times the best move changed for each iteration
252 Value ValueByIteration[PLY_MAX_PLUS_2];
253 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
255 // Search window management
261 // Time managment variables
262 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
263 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
264 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
269 std::ofstream LogFile;
271 // Multi-threads manager object
272 ThreadsManager ThreadsMgr;
274 // Node counters, used only by thread[0] but try to keep in different cache
275 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
276 bool SendSearchedNodes;
278 int NodesBetweenPolls = 30000;
285 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
286 Value root_search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, RootMoveList& rml);
288 template <NodeType PvNode, bool SpNode>
289 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
291 template <NodeType PvNode>
292 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
294 template <NodeType PvNode>
295 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
297 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
298 : search<PvNode, false>(pos, ss, alpha, beta, depth, ply);
301 template <NodeType PvNode>
302 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
304 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
305 bool connected_moves(const Position& pos, Move m1, Move m2);
306 bool value_is_mate(Value value);
307 Value value_to_tt(Value v, int ply);
308 Value value_from_tt(Value v, int ply);
309 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
310 bool connected_threat(const Position& pos, Move m, Move threat);
311 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
312 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
313 void update_killers(Move m, Move killers[]);
314 void update_gains(const Position& pos, Move move, Value before, Value after);
316 int current_search_time();
317 std::string value_to_uci(Value v);
318 int nps(const Position& pos);
319 void poll(const Position& pos);
320 void wait_for_stop_or_ponderhit();
321 void init_ss_array(SearchStack* ss, int size);
323 #if !defined(_MSC_VER)
324 void* init_thread(void* threadID);
326 DWORD WINAPI init_thread(LPVOID threadID);
336 /// init_threads(), exit_threads() and nodes_searched() are helpers to
337 /// give accessibility to some TM methods from outside of current file.
339 void init_threads() { ThreadsMgr.init_threads(); }
340 void exit_threads() { ThreadsMgr.exit_threads(); }
343 /// init_search() is called during startup. It initializes various lookup tables
347 int d; // depth (ONE_PLY == 2)
348 int hd; // half depth (ONE_PLY == 1)
351 // Init reductions array
352 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
354 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
355 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
356 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
357 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
360 // Init futility margins array
361 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
362 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
364 // Init futility move count array
365 for (d = 0; d < 32; d++)
366 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
370 /// perft() is our utility to verify move generation is bug free. All the legal
371 /// moves up to given depth are generated and counted and the sum returned.
373 int64_t perft(Position& pos, Depth depth)
375 MoveStack mlist[MOVES_MAX];
380 // Generate all legal moves
381 MoveStack* last = generate_moves(pos, mlist);
383 // If we are at the last ply we don't need to do and undo
384 // the moves, just to count them.
385 if (depth <= ONE_PLY)
386 return int(last - mlist);
388 // Loop through all legal moves
390 for (MoveStack* cur = mlist; cur != last; cur++)
393 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
394 sum += perft(pos, depth - ONE_PLY);
401 /// think() is the external interface to Stockfish's search, and is called when
402 /// the program receives the UCI 'go' command. It initializes various
403 /// search-related global variables, and calls root_search(). It returns false
404 /// when a quit command is received during the search.
406 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
407 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
409 // Initialize global search variables
410 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
412 SearchStartTime = get_system_time();
413 ExactMaxTime = maxTime;
416 InfiniteSearch = infinite;
418 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
420 // Look for a book move, only during games, not tests
421 if (UseTimeManagement && Options["OwnBook"].value<bool>())
423 if (Options["Book File"].value<std::string>() != OpeningBook.file_name())
424 OpeningBook.open(Options["Book File"].value<std::string>());
426 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
427 if (bookMove != MOVE_NONE)
430 wait_for_stop_or_ponderhit();
432 cout << "bestmove " << bookMove << endl;
437 // Read UCI option values
438 TT.set_size(Options["Hash"].value<int>());
439 if (Options["Clear Hash"].value<bool>())
441 Options["Clear Hash"].set_value("false");
445 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
446 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
447 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
448 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
449 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
450 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
451 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
452 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
453 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
454 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
455 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
456 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
457 MultiPV = Options["MultiPV"].value<int>();
458 UseLogFile = Options["Use Search Log"].value<bool>();
460 read_evaluation_uci_options(pos.side_to_move());
462 // Set the number of active threads
463 ThreadsMgr.read_uci_options();
464 init_eval(ThreadsMgr.active_threads());
466 // Wake up needed threads
467 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
468 ThreadsMgr.wake_sleeping_thread(i);
471 int myTime = time[pos.side_to_move()];
472 int myIncrement = increment[pos.side_to_move()];
473 if (UseTimeManagement)
474 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
476 // Set best NodesBetweenPolls interval to avoid lagging under
477 // heavy time pressure.
479 NodesBetweenPolls = Min(MaxNodes, 30000);
480 else if (myTime && myTime < 1000)
481 NodesBetweenPolls = 1000;
482 else if (myTime && myTime < 5000)
483 NodesBetweenPolls = 5000;
485 NodesBetweenPolls = 30000;
487 // Write search information to log file
490 std::string name = Options["Search Log Filename"].value<std::string>();
491 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
493 LogFile << "Searching: " << pos.to_fen()
494 << "\ninfinite: " << infinite
495 << " ponder: " << ponder
496 << " time: " << myTime
497 << " increment: " << myIncrement
498 << " moves to go: " << movesToGo << endl;
501 // We're ready to start thinking. Call the iterative deepening loop function
502 Move ponderMove = MOVE_NONE;
503 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
505 // Print final search statistics
506 cout << "info nodes " << pos.nodes_searched()
507 << " nps " << nps(pos)
508 << " time " << current_search_time() << endl;
512 LogFile << "\nNodes: " << pos.nodes_searched()
513 << "\nNodes/second: " << nps(pos)
514 << "\nBest move: " << move_to_san(pos, bestMove);
517 pos.do_move(bestMove, st);
518 LogFile << "\nPonder move: "
519 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
522 // Return from think() with unchanged position
523 pos.undo_move(bestMove);
528 // This makes all the threads to go to sleep
529 ThreadsMgr.set_active_threads(1);
531 // If we are pondering or in infinite search, we shouldn't print the
532 // best move before we are told to do so.
533 if (!StopRequest && (Pondering || InfiniteSearch))
534 wait_for_stop_or_ponderhit();
536 // Could be both MOVE_NONE when searching on a stalemate position
537 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
545 // id_loop() is the main iterative deepening loop. It calls root_search
546 // repeatedly with increasing depth until the allocated thinking time has
547 // been consumed, the user stops the search, or the maximum search depth is
550 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
552 SearchStack ss[PLY_MAX_PLUS_2];
554 Move EasyMove = MOVE_NONE;
555 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
557 // Moves to search are verified, scored and sorted
558 RootMoveList rml(pos, searchMoves);
560 // Handle special case of searching on a mate/stale position
563 Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
565 cout << "info depth " << 1
566 << " score " << value_to_uci(s) << endl;
574 init_ss_array(ss, PLY_MAX_PLUS_2);
575 ValueByIteration[1] = rml[0].pv_score;
578 // Send initial RootMoveList scoring (iteration 1)
579 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
580 << "info depth " << Iteration
581 << "\n" << rml[0].pv_info_to_uci(pos, alpha, beta) << endl;
583 // Is one move significantly better than others after initial scoring ?
585 || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
586 EasyMove = rml[0].pv[0];
588 // Iterative deepening loop
589 while (Iteration < PLY_MAX)
591 // Initialize iteration
593 BestMoveChangesByIteration[Iteration] = 0;
595 cout << "info depth " << Iteration << endl;
597 // Calculate dynamic aspiration window based on previous iterations
598 if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
600 int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
601 int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
603 AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
604 AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
606 alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
607 beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
610 depth = (Iteration - 2) * ONE_PLY + InitialDepth;
612 // Search to the current depth, rml is updated and sorted
613 value = root_search(pos, ss, alpha, beta, depth, rml);
616 break; // Value cannot be trusted. Break out immediately!
618 //Save info about search result
619 ValueByIteration[Iteration] = value;
621 // Drop the easy move if differs from the new best move
622 if (rml[0].pv[0] != EasyMove)
623 EasyMove = MOVE_NONE;
625 if (UseTimeManagement)
628 bool stopSearch = false;
630 // Stop search early if there is only a single legal move,
631 // we search up to Iteration 6 anyway to get a proper score.
632 if (Iteration >= 6 && rml.size() == 1)
635 // Stop search early when the last two iterations returned a mate score
637 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
638 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
641 // Stop search early if one move seems to be much better than the others
643 && EasyMove == rml[0].pv[0]
644 && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
645 && current_search_time() > TimeMgr.available_time() / 16)
646 ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
647 && current_search_time() > TimeMgr.available_time() / 32)))
650 // Add some extra time if the best move has changed during the last two iterations
651 if (Iteration > 5 && Iteration <= 50)
652 TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
653 BestMoveChangesByIteration[Iteration-1]);
655 // Stop search if most of MaxSearchTime is consumed at the end of the
656 // iteration. We probably don't have enough time to search the first
657 // move at the next iteration anyway.
658 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
664 StopOnPonderhit = true;
670 if (MaxDepth && Iteration >= MaxDepth)
674 *ponderMove = rml[0].pv[1];
679 // root_search() is the function which searches the root node. It is
680 // similar to search_pv except that it prints some information to the
681 // standard output and handles the fail low/high loops.
683 Value root_search(Position& pos, SearchStack* ss, Value alpha,
684 Value beta, Depth depth, RootMoveList& rml) {
686 Move movesSearched[MOVES_MAX];
691 Value value, oldAlpha;
692 RootMoveList::iterator rm;
693 bool isCheck, moveIsCheck, captureOrPromotion, dangerous, isPvMove;
694 int moveCount, researchCountFH, researchCountFL;
696 researchCountFH = researchCountFL = 0;
698 isCheck = pos.is_check();
700 // Step 1. Initialize node (polling is omitted at root)
701 ss->currentMove = ss->bestMove = MOVE_NONE;
703 // Step 2. Check for aborted search (omitted at root)
704 // Step 3. Mate distance pruning (omitted at root)
705 // Step 4. Transposition table lookup (omitted at root)
707 // Step 5. Evaluate the position statically
708 // At root we do this only to get reference value for child nodes
709 ss->evalMargin = VALUE_NONE;
710 ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
712 // Step 6. Razoring (omitted at root)
713 // Step 7. Static null move pruning (omitted at root)
714 // Step 8. Null move search with verification search (omitted at root)
715 // Step 9. Internal iterative deepening (omitted at root)
717 // Step extra. Fail low loop
718 // We start with small aspiration window and in case of fail low, we research
719 // with bigger window until we are not failing low anymore.
722 // Sort the moves before to (re)search
723 rml.set_non_pv_scores(pos, rml[0].pv[0], ss);
727 // Step 10. Loop through all moves in the root move list
728 for (rm = rml.begin(); rm != rml.end() && !StopRequest; ++rm)
730 // This is used by time management
731 FirstRootMove = (rm == rml.begin());
733 // Save the current node count before the move is searched
734 nodes = pos.nodes_searched();
736 // If it's time to send nodes info, do it here where we have the
737 // correct accumulated node counts searched by each thread.
738 if (SendSearchedNodes)
740 SendSearchedNodes = false;
741 cout << "info nodes " << nodes
742 << " nps " << nps(pos)
743 << " time " << current_search_time() << endl;
746 // Pick the next root move, and print the move and the move number to
747 // the standard output.
748 move = ss->currentMove = rm->pv[0];
749 movesSearched[moveCount++] = move;
750 isPvMove = (moveCount <= MultiPV);
752 if (current_search_time() >= 1000)
753 cout << "info currmove " << move
754 << " currmovenumber " << moveCount << endl;
756 moveIsCheck = pos.move_is_check(move);
757 captureOrPromotion = pos.move_is_capture_or_promotion(move);
759 // Step 11. Decide the new search depth
760 ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
761 newDepth = depth + ext;
763 // Step 12. Futility pruning (omitted at root)
765 // Step extra. Fail high loop
766 // If move fails high, we research with bigger window until we are not failing
768 value = -VALUE_INFINITE;
772 // Step 13. Make the move
773 pos.do_move(move, st, ci, moveIsCheck);
775 // Step extra. pv search
776 // We do pv search for PV moves and when failing high
777 if (isPvMove || value > alpha)
779 // Aspiration window is disabled in multi-pv case
781 alpha = -VALUE_INFINITE;
783 // Full depth PV search, done on first move or after a fail high
784 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
788 // Step 14. Reduced search
789 // if the move fails high will be re-searched at full depth
790 bool doFullDepthSearch = true;
792 if ( depth >= 3 * ONE_PLY
794 && !captureOrPromotion
795 && !move_is_castle(move))
797 ss->reduction = reduction<PV>(depth, moveCount - MultiPV + 1);
800 assert(newDepth-ss->reduction >= ONE_PLY);
802 // Reduced depth non-pv search using alpha as upperbound
803 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1);
804 doFullDepthSearch = (value > alpha);
806 ss->reduction = DEPTH_ZERO; // Restore original reduction
809 // Step 15. Full depth search
810 if (doFullDepthSearch)
812 // Full depth non-pv search using alpha as upperbound
813 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
815 // If we are above alpha then research at same depth but as PV
816 // to get a correct score or eventually a fail high above beta.
818 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
822 // Step 16. Undo move
825 // Can we exit fail high loop ?
826 if (StopRequest || value < beta)
829 // We are failing high and going to do a research. It's important to update
830 // the score before research in case we run out of time while researching.
832 rm->pv_score = value;
833 rm->extract_pv_from_tt(pos);
835 // Update killers and history only for non capture moves that fails high
836 if (!pos.move_is_capture_or_promotion(move))
838 update_history(pos, move, depth, movesSearched, moveCount);
839 update_killers(move, ss->killers);
842 // Inform GUI that PV has changed
843 cout << rm->pv_info_to_uci(pos, alpha, beta) << endl;
845 // Prepare for a research after a fail high, each time with a wider window
846 beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
849 } // End of fail high loop
851 // Finished searching the move. If AbortSearch is true, the search
852 // was aborted because the user interrupted the search or because we
853 // ran out of time. In this case, the return value of the search cannot
854 // be trusted, and we break out of the loop without updating the best
859 // Remember searched nodes counts for this move
860 rm->nodes += pos.nodes_searched() - nodes;
862 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
863 assert(value < beta);
865 // Step 17. Check for new best move
866 if (!isPvMove && value <= alpha)
867 rm->pv_score = -VALUE_INFINITE;
870 // PV move or new best move!
874 rm->pv_score = value;
875 rm->extract_pv_from_tt(pos);
877 // We record how often the best move has been changed in each
878 // iteration. This information is used for time managment: When
879 // the best move changes frequently, we allocate some more time.
880 if (!isPvMove && MultiPV == 1)
881 BestMoveChangesByIteration[Iteration]++;
883 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
884 // requires we send all the PV lines properly sorted.
885 rml.sort_multipv(moveCount);
887 for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++)
888 cout << rml[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
890 // Update alpha. In multi-pv we don't use aspiration window
893 // Raise alpha to setup proper non-pv search upper bound
897 else // Set alpha equal to minimum score among the PV lines
898 alpha = rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
900 } // PV move or new best move
902 assert(alpha >= oldAlpha);
904 AspirationFailLow = (alpha == oldAlpha);
906 if (AspirationFailLow && StopOnPonderhit)
907 StopOnPonderhit = false;
911 // Can we exit fail low loop ?
912 if (StopRequest || !AspirationFailLow)
915 // Prepare for a research after a fail low, each time with a wider window
916 oldAlpha = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
921 // Sort the moves before to return
924 // Write PV lines to transposition table, in case the relevant entries
925 // have been overwritten during the search.
926 for (int i = 0; i < Min(MultiPV, (int)rml.size()); i++)
927 rml[i].insert_pv_in_tt(pos);
933 // search<>() is the main search function for both PV and non-PV nodes and for
934 // normal and SplitPoint nodes. When called just after a split point the search
935 // is simpler because we have already probed the hash table, done a null move
936 // search, and searched the first move before splitting, we don't have to repeat
937 // all this work again. We also don't need to store anything to the hash table
938 // here: This is taken care of after we return from the split point.
940 template <NodeType PvNode, bool SpNode>
941 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
943 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
944 assert(beta > alpha && beta <= VALUE_INFINITE);
945 assert(PvNode || alpha == beta - 1);
946 assert(ply > 0 && ply < PLY_MAX);
947 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
949 Move movesSearched[MOVES_MAX];
953 Move ttMove, move, excludedMove, threatMove;
956 Value bestValue, value, oldAlpha;
957 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
958 bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
959 bool mateThreat = false;
961 int threadID = pos.thread();
962 SplitPoint* sp = NULL;
963 refinedValue = bestValue = value = -VALUE_INFINITE;
965 isCheck = pos.is_check();
971 ttMove = excludedMove = MOVE_NONE;
972 threatMove = sp->threatMove;
973 mateThreat = sp->mateThreat;
974 goto split_point_start;
976 else {} // Hack to fix icc's "statement is unreachable" warning
978 // Step 1. Initialize node and poll. Polling can abort search
979 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
980 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
982 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
988 // Step 2. Check for aborted search and immediate draw
990 || ThreadsMgr.cutoff_at_splitpoint(threadID)
992 || ply >= PLY_MAX - 1)
995 // Step 3. Mate distance pruning
996 alpha = Max(value_mated_in(ply), alpha);
997 beta = Min(value_mate_in(ply+1), beta);
1001 // Step 4. Transposition table lookup
1003 // We don't want the score of a partial search to overwrite a previous full search
1004 // TT value, so we use a different position key in case of an excluded move exists.
1005 excludedMove = ss->excludedMove;
1006 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
1008 tte = TT.retrieve(posKey);
1009 ttMove = tte ? tte->move() : MOVE_NONE;
1011 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
1012 // This is to avoid problems in the following areas:
1014 // * Repetition draw detection
1015 // * Fifty move rule detection
1016 // * Searching for a mate
1017 // * Printing of full PV line
1018 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
1021 ss->bestMove = ttMove; // Can be MOVE_NONE
1022 return value_from_tt(tte->value(), ply);
1025 // Step 5. Evaluate the position statically and
1026 // update gain statistics of parent move.
1028 ss->eval = ss->evalMargin = VALUE_NONE;
1031 assert(tte->static_value() != VALUE_NONE);
1033 ss->eval = tte->static_value();
1034 ss->evalMargin = tte->static_value_margin();
1035 refinedValue = refine_eval(tte, ss->eval, ply);
1039 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
1040 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
1043 // Save gain for the parent non-capture move
1044 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1046 // Step 6. Razoring (is omitted in PV nodes)
1048 && depth < RazorDepth
1050 && refinedValue < beta - razor_margin(depth)
1051 && ttMove == MOVE_NONE
1052 && !value_is_mate(beta)
1053 && !pos.has_pawn_on_7th(pos.side_to_move()))
1055 Value rbeta = beta - razor_margin(depth);
1056 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
1058 // Logically we should return (v + razor_margin(depth)), but
1059 // surprisingly this did slightly weaker in tests.
1063 // Step 7. Static null move pruning (is omitted in PV nodes)
1064 // We're betting that the opponent doesn't have a move that will reduce
1065 // the score by more than futility_margin(depth) if we do a null move.
1067 && !ss->skipNullMove
1068 && depth < RazorDepth
1070 && refinedValue >= beta + futility_margin(depth, 0)
1071 && !value_is_mate(beta)
1072 && pos.non_pawn_material(pos.side_to_move()))
1073 return refinedValue - futility_margin(depth, 0);
1075 // Step 8. Null move search with verification search (is omitted in PV nodes)
1077 && !ss->skipNullMove
1080 && refinedValue >= beta
1081 && !value_is_mate(beta)
1082 && pos.non_pawn_material(pos.side_to_move()))
1084 ss->currentMove = MOVE_NULL;
1086 // Null move dynamic reduction based on depth
1087 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
1089 // Null move dynamic reduction based on value
1090 if (refinedValue - beta > PawnValueMidgame)
1093 pos.do_null_move(st);
1094 (ss+1)->skipNullMove = true;
1095 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
1096 (ss+1)->skipNullMove = false;
1097 pos.undo_null_move();
1099 if (nullValue >= beta)
1101 // Do not return unproven mate scores
1102 if (nullValue >= value_mate_in(PLY_MAX))
1105 if (depth < 6 * ONE_PLY)
1108 // Do verification search at high depths
1109 ss->skipNullMove = true;
1110 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
1111 ss->skipNullMove = false;
1118 // The null move failed low, which means that we may be faced with
1119 // some kind of threat. If the previous move was reduced, check if
1120 // the move that refuted the null move was somehow connected to the
1121 // move which was reduced. If a connection is found, return a fail
1122 // low score (which will cause the reduced move to fail high in the
1123 // parent node, which will trigger a re-search with full depth).
1124 if (nullValue == value_mated_in(ply + 2))
1127 threatMove = (ss+1)->bestMove;
1128 if ( depth < ThreatDepth
1129 && (ss-1)->reduction
1130 && threatMove != MOVE_NONE
1131 && connected_moves(pos, (ss-1)->currentMove, threatMove))
1136 // Step 9. Internal iterative deepening
1137 if ( depth >= IIDDepth[PvNode]
1138 && ttMove == MOVE_NONE
1139 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
1141 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
1143 ss->skipNullMove = true;
1144 search<PvNode>(pos, ss, alpha, beta, d, ply);
1145 ss->skipNullMove = false;
1147 ttMove = ss->bestMove;
1148 tte = TT.retrieve(posKey);
1151 // Expensive mate threat detection (only for PV nodes)
1153 mateThreat = pos.has_mate_threat();
1155 split_point_start: // At split points actual search starts from here
1157 // Initialize a MovePicker object for the current position
1158 // FIXME currently MovePicker() c'tor is needless called also in SplitPoint
1159 MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1160 MovePicker& mp = SpNode ? *sp->mp : mpBase;
1162 ss->bestMove = MOVE_NONE;
1163 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1164 futilityBase = ss->eval + ss->evalMargin;
1165 singularExtensionNode = !SpNode
1166 && depth >= SingularExtensionDepth[PvNode]
1169 && !excludedMove // Do not allow recursive singular extension search
1170 && (tte->type() & VALUE_TYPE_LOWER)
1171 && tte->depth() >= depth - 3 * ONE_PLY;
1174 lock_grab(&(sp->lock));
1175 bestValue = sp->bestValue;
1178 // Step 10. Loop through moves
1179 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1180 while ( bestValue < beta
1181 && (move = mp.get_next_move()) != MOVE_NONE
1182 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1184 assert(move_is_ok(move));
1188 moveCount = ++sp->moveCount;
1189 lock_release(&(sp->lock));
1191 else if (move == excludedMove)
1194 movesSearched[moveCount++] = move;
1196 moveIsCheck = pos.move_is_check(move, ci);
1197 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1199 // Step 11. Decide the new search depth
1200 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1202 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1203 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1204 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1205 // lower then ttValue minus a margin then we extend ttMove.
1206 if ( singularExtensionNode
1207 && move == tte->move()
1210 Value ttValue = value_from_tt(tte->value(), ply);
1212 if (abs(ttValue) < VALUE_KNOWN_WIN)
1214 Value b = ttValue - SingularExtensionMargin;
1215 ss->excludedMove = move;
1216 ss->skipNullMove = true;
1217 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1218 ss->skipNullMove = false;
1219 ss->excludedMove = MOVE_NONE;
1220 ss->bestMove = MOVE_NONE;
1226 // Update current move (this must be done after singular extension search)
1227 ss->currentMove = move;
1228 newDepth = depth - ONE_PLY + ext;
1230 // Step 12. Futility pruning (is omitted in PV nodes)
1232 && !captureOrPromotion
1236 && !move_is_castle(move))
1238 // Move count based pruning
1239 if ( moveCount >= futility_move_count(depth)
1240 && !(threatMove && connected_threat(pos, move, threatMove))
1241 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1244 lock_grab(&(sp->lock));
1249 // Value based pruning
1250 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1251 // but fixing this made program slightly weaker.
1252 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1253 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1254 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1256 if (futilityValueScaled < beta)
1260 lock_grab(&(sp->lock));
1261 if (futilityValueScaled > sp->bestValue)
1262 sp->bestValue = bestValue = futilityValueScaled;
1264 else if (futilityValueScaled > bestValue)
1265 bestValue = futilityValueScaled;
1270 // Prune moves with negative SEE at low depths
1271 if ( predictedDepth < 2 * ONE_PLY
1272 && bestValue > value_mated_in(PLY_MAX)
1273 && pos.see_sign(move) < 0)
1276 lock_grab(&(sp->lock));
1282 // Step 13. Make the move
1283 pos.do_move(move, st, ci, moveIsCheck);
1285 // Step extra. pv search (only in PV nodes)
1286 // The first move in list is the expected PV
1287 if (PvNode && moveCount == 1)
1288 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1291 // Step 14. Reduced depth search
1292 // If the move fails high will be re-searched at full depth.
1293 bool doFullDepthSearch = true;
1295 if ( depth >= 3 * ONE_PLY
1296 && !captureOrPromotion
1298 && !move_is_castle(move)
1299 && ss->killers[0] != move
1300 && ss->killers[1] != move)
1302 ss->reduction = reduction<PvNode>(depth, moveCount);
1306 alpha = SpNode ? sp->alpha : alpha;
1307 Depth d = newDepth - ss->reduction;
1308 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1310 doFullDepthSearch = (value > alpha);
1312 ss->reduction = DEPTH_ZERO; // Restore original reduction
1315 // Step 15. Full depth search
1316 if (doFullDepthSearch)
1318 alpha = SpNode ? sp->alpha : alpha;
1319 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1321 // Step extra. pv search (only in PV nodes)
1322 // Search only for possible new PV nodes, if instead value >= beta then
1323 // parent node fails low with value <= alpha and tries another move.
1324 if (PvNode && value > alpha && value < beta)
1325 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1329 // Step 16. Undo move
1330 pos.undo_move(move);
1332 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1334 // Step 17. Check for new best move
1337 lock_grab(&(sp->lock));
1338 bestValue = sp->bestValue;
1342 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1347 sp->bestValue = value;
1351 if (PvNode && value < beta) // We want always alpha < beta
1359 sp->betaCutoff = true;
1361 if (value == value_mate_in(ply + 1))
1362 ss->mateKiller = move;
1364 ss->bestMove = move;
1367 sp->parentSstack->bestMove = move;
1371 // Step 18. Check for split
1373 && depth >= ThreadsMgr.min_split_depth()
1374 && ThreadsMgr.active_threads() > 1
1376 && ThreadsMgr.available_thread_exists(threadID)
1378 && !ThreadsMgr.cutoff_at_splitpoint(threadID)
1380 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1381 threatMove, mateThreat, moveCount, &mp, PvNode);
1384 // Step 19. Check for mate and stalemate
1385 // All legal moves have been searched and if there are
1386 // no legal moves, it must be mate or stalemate.
1387 // If one move was excluded return fail low score.
1388 if (!SpNode && !moveCount)
1389 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1391 // Step 20. Update tables
1392 // If the search is not aborted, update the transposition table,
1393 // history counters, and killer moves.
1394 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1396 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1397 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1398 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1400 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1402 // Update killers and history only for non capture moves that fails high
1403 if ( bestValue >= beta
1404 && !pos.move_is_capture_or_promotion(move))
1406 update_history(pos, move, depth, movesSearched, moveCount);
1407 update_killers(move, ss->killers);
1413 // Here we have the lock still grabbed
1414 sp->slaves[threadID] = 0;
1415 sp->nodes += pos.nodes_searched();
1416 lock_release(&(sp->lock));
1419 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1424 // qsearch() is the quiescence search function, which is called by the main
1425 // search function when the remaining depth is zero (or, to be more precise,
1426 // less than ONE_PLY).
1428 template <NodeType PvNode>
1429 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1431 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1432 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1433 assert(PvNode || alpha == beta - 1);
1435 assert(ply > 0 && ply < PLY_MAX);
1436 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1440 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1441 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1444 Value oldAlpha = alpha;
1446 ss->bestMove = ss->currentMove = MOVE_NONE;
1448 // Check for an instant draw or maximum ply reached
1449 if (pos.is_draw() || ply >= PLY_MAX - 1)
1452 // Decide whether or not to include checks, this fixes also the type of
1453 // TT entry depth that we are going to use. Note that in qsearch we use
1454 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1455 isCheck = pos.is_check();
1456 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1458 // Transposition table lookup. At PV nodes, we don't use the TT for
1459 // pruning, but only for move ordering.
1460 tte = TT.retrieve(pos.get_key());
1461 ttMove = (tte ? tte->move() : MOVE_NONE);
1463 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1465 ss->bestMove = ttMove; // Can be MOVE_NONE
1466 return value_from_tt(tte->value(), ply);
1469 // Evaluate the position statically
1472 bestValue = futilityBase = -VALUE_INFINITE;
1473 ss->eval = evalMargin = VALUE_NONE;
1474 enoughMaterial = false;
1480 assert(tte->static_value() != VALUE_NONE);
1482 evalMargin = tte->static_value_margin();
1483 ss->eval = bestValue = tte->static_value();
1486 ss->eval = bestValue = evaluate(pos, evalMargin);
1488 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1490 // Stand pat. Return immediately if static value is at least beta
1491 if (bestValue >= beta)
1494 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1499 if (PvNode && bestValue > alpha)
1502 // Futility pruning parameters, not needed when in check
1503 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1504 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1507 // Initialize a MovePicker object for the current position, and prepare
1508 // to search the moves. Because the depth is <= 0 here, only captures,
1509 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1511 MovePicker mp(pos, ttMove, depth, H);
1514 // Loop through the moves until no moves remain or a beta cutoff occurs
1515 while ( alpha < beta
1516 && (move = mp.get_next_move()) != MOVE_NONE)
1518 assert(move_is_ok(move));
1520 moveIsCheck = pos.move_is_check(move, ci);
1528 && !move_is_promotion(move)
1529 && !pos.move_is_passed_pawn_push(move))
1531 futilityValue = futilityBase
1532 + pos.endgame_value_of_piece_on(move_to(move))
1533 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1535 if (futilityValue < alpha)
1537 if (futilityValue > bestValue)
1538 bestValue = futilityValue;
1543 // Detect non-capture evasions that are candidate to be pruned
1544 evasionPrunable = isCheck
1545 && bestValue > value_mated_in(PLY_MAX)
1546 && !pos.move_is_capture(move)
1547 && !pos.can_castle(pos.side_to_move());
1549 // Don't search moves with negative SEE values
1551 && (!isCheck || evasionPrunable)
1553 && !move_is_promotion(move)
1554 && pos.see_sign(move) < 0)
1557 // Don't search useless checks
1562 && !pos.move_is_capture_or_promotion(move)
1563 && ss->eval + PawnValueMidgame / 4 < beta
1564 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1566 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1567 bestValue = ss->eval + PawnValueMidgame / 4;
1572 // Update current move
1573 ss->currentMove = move;
1575 // Make and search the move
1576 pos.do_move(move, st, ci, moveIsCheck);
1577 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1578 pos.undo_move(move);
1580 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1583 if (value > bestValue)
1589 ss->bestMove = move;
1594 // All legal moves have been searched. A special case: If we're in check
1595 // and no legal moves were found, it is checkmate.
1596 if (isCheck && bestValue == -VALUE_INFINITE)
1597 return value_mated_in(ply);
1599 // Update transposition table
1600 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1601 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1603 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1609 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1610 // bestValue is updated only when returning false because in that case move
1613 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1615 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1616 Square from, to, ksq, victimSq;
1619 Value futilityValue, bv = *bestValue;
1621 from = move_from(move);
1623 them = opposite_color(pos.side_to_move());
1624 ksq = pos.king_square(them);
1625 kingAtt = pos.attacks_from<KING>(ksq);
1626 pc = pos.piece_on(from);
1628 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1629 oldAtt = pos.attacks_from(pc, from, occ);
1630 newAtt = pos.attacks_from(pc, to, occ);
1632 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1633 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1635 if (!(b && (b & (b - 1))))
1638 // Rule 2. Queen contact check is very dangerous
1639 if ( type_of_piece(pc) == QUEEN
1640 && bit_is_set(kingAtt, to))
1643 // Rule 3. Creating new double threats with checks
1644 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1648 victimSq = pop_1st_bit(&b);
1649 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1651 // Note that here we generate illegal "double move"!
1652 if ( futilityValue >= beta
1653 && pos.see_sign(make_move(from, victimSq)) >= 0)
1656 if (futilityValue > bv)
1660 // Update bestValue only if check is not dangerous (because we will prune the move)
1666 // connected_moves() tests whether two moves are 'connected' in the sense
1667 // that the first move somehow made the second move possible (for instance
1668 // if the moving piece is the same in both moves). The first move is assumed
1669 // to be the move that was made to reach the current position, while the
1670 // second move is assumed to be a move from the current position.
1672 bool connected_moves(const Position& pos, Move m1, Move m2) {
1674 Square f1, t1, f2, t2;
1677 assert(m1 && move_is_ok(m1));
1678 assert(m2 && move_is_ok(m2));
1680 // Case 1: The moving piece is the same in both moves
1686 // Case 2: The destination square for m2 was vacated by m1
1692 // Case 3: Moving through the vacated square
1693 if ( piece_is_slider(pos.piece_on(f2))
1694 && bit_is_set(squares_between(f2, t2), f1))
1697 // Case 4: The destination square for m2 is defended by the moving piece in m1
1698 p = pos.piece_on(t1);
1699 if (bit_is_set(pos.attacks_from(p, t1), t2))
1702 // Case 5: Discovered check, checking piece is the piece moved in m1
1703 if ( piece_is_slider(p)
1704 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1705 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1707 // discovered_check_candidates() works also if the Position's side to
1708 // move is the opposite of the checking piece.
1709 Color them = opposite_color(pos.side_to_move());
1710 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1712 if (bit_is_set(dcCandidates, f2))
1719 // value_is_mate() checks if the given value is a mate one eventually
1720 // compensated for the ply.
1722 bool value_is_mate(Value value) {
1724 assert(abs(value) <= VALUE_INFINITE);
1726 return value <= value_mated_in(PLY_MAX)
1727 || value >= value_mate_in(PLY_MAX);
1731 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1732 // "plies to mate from the current ply". Non-mate scores are unchanged.
1733 // The function is called before storing a value to the transposition table.
1735 Value value_to_tt(Value v, int ply) {
1737 if (v >= value_mate_in(PLY_MAX))
1740 if (v <= value_mated_in(PLY_MAX))
1747 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1748 // the transposition table to a mate score corrected for the current ply.
1750 Value value_from_tt(Value v, int ply) {
1752 if (v >= value_mate_in(PLY_MAX))
1755 if (v <= value_mated_in(PLY_MAX))
1762 // extension() decides whether a move should be searched with normal depth,
1763 // or with extended depth. Certain classes of moves (checking moves, in
1764 // particular) are searched with bigger depth than ordinary moves and in
1765 // any case are marked as 'dangerous'. Note that also if a move is not
1766 // extended, as example because the corresponding UCI option is set to zero,
1767 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1768 template <NodeType PvNode>
1769 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1770 bool singleEvasion, bool mateThreat, bool* dangerous) {
1772 assert(m != MOVE_NONE);
1774 Depth result = DEPTH_ZERO;
1775 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1779 if (moveIsCheck && pos.see_sign(m) >= 0)
1780 result += CheckExtension[PvNode];
1783 result += SingleEvasionExtension[PvNode];
1786 result += MateThreatExtension[PvNode];
1789 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1791 Color c = pos.side_to_move();
1792 if (relative_rank(c, move_to(m)) == RANK_7)
1794 result += PawnPushTo7thExtension[PvNode];
1797 if (pos.pawn_is_passed(c, move_to(m)))
1799 result += PassedPawnExtension[PvNode];
1804 if ( captureOrPromotion
1805 && pos.type_of_piece_on(move_to(m)) != PAWN
1806 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1807 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1808 && !move_is_promotion(m)
1811 result += PawnEndgameExtension[PvNode];
1816 && captureOrPromotion
1817 && pos.type_of_piece_on(move_to(m)) != PAWN
1818 && pos.see_sign(m) >= 0)
1820 result += ONE_PLY / 2;
1824 return Min(result, ONE_PLY);
1828 // connected_threat() tests whether it is safe to forward prune a move or if
1829 // is somehow coonected to the threat move returned by null search.
1831 bool connected_threat(const Position& pos, Move m, Move threat) {
1833 assert(move_is_ok(m));
1834 assert(threat && move_is_ok(threat));
1835 assert(!pos.move_is_check(m));
1836 assert(!pos.move_is_capture_or_promotion(m));
1837 assert(!pos.move_is_passed_pawn_push(m));
1839 Square mfrom, mto, tfrom, tto;
1841 mfrom = move_from(m);
1843 tfrom = move_from(threat);
1844 tto = move_to(threat);
1846 // Case 1: Don't prune moves which move the threatened piece
1850 // Case 2: If the threatened piece has value less than or equal to the
1851 // value of the threatening piece, don't prune move which defend it.
1852 if ( pos.move_is_capture(threat)
1853 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1854 || pos.type_of_piece_on(tfrom) == KING)
1855 && pos.move_attacks_square(m, tto))
1858 // Case 3: If the moving piece in the threatened move is a slider, don't
1859 // prune safe moves which block its ray.
1860 if ( piece_is_slider(pos.piece_on(tfrom))
1861 && bit_is_set(squares_between(tfrom, tto), mto)
1862 && pos.see_sign(m) >= 0)
1869 // ok_to_use_TT() returns true if a transposition table score
1870 // can be used at a given point in search.
1872 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1874 Value v = value_from_tt(tte->value(), ply);
1876 return ( tte->depth() >= depth
1877 || v >= Max(value_mate_in(PLY_MAX), beta)
1878 || v < Min(value_mated_in(PLY_MAX), beta))
1880 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1881 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1885 // refine_eval() returns the transposition table score if
1886 // possible otherwise falls back on static position evaluation.
1888 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1892 Value v = value_from_tt(tte->value(), ply);
1894 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1895 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1902 // update_history() registers a good move that produced a beta-cutoff
1903 // in history and marks as failures all the other moves of that ply.
1905 void update_history(const Position& pos, Move move, Depth depth,
1906 Move movesSearched[], int moveCount) {
1909 H.success(pos.piece_on(move_from(move)), move_to(move), depth);
1911 for (int i = 0; i < moveCount - 1; i++)
1913 m = movesSearched[i];
1917 if (!pos.move_is_capture_or_promotion(m))
1918 H.failure(pos.piece_on(move_from(m)), move_to(m), depth);
1923 // update_killers() add a good move that produced a beta-cutoff
1924 // among the killer moves of that ply.
1926 void update_killers(Move m, Move killers[]) {
1928 if (m == killers[0])
1931 killers[1] = killers[0];
1936 // update_gains() updates the gains table of a non-capture move given
1937 // the static position evaluation before and after the move.
1939 void update_gains(const Position& pos, Move m, Value before, Value after) {
1942 && before != VALUE_NONE
1943 && after != VALUE_NONE
1944 && pos.captured_piece_type() == PIECE_TYPE_NONE
1945 && !move_is_special(m))
1946 H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1950 // init_ss_array() does a fast reset of the first entries of a SearchStack
1951 // array and of all the excludedMove and skipNullMove entries.
1953 void init_ss_array(SearchStack* ss, int size) {
1955 for (int i = 0; i < size; i++, ss++)
1957 ss->excludedMove = MOVE_NONE;
1958 ss->skipNullMove = false;
1959 ss->reduction = DEPTH_ZERO;
1963 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
1968 // value_to_uci() converts a value to a string suitable for use with the UCI
1969 // protocol specifications:
1971 // cp <x> The score from the engine's point of view in centipawns.
1972 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1973 // use negative values for y.
1975 std::string value_to_uci(Value v) {
1977 std::stringstream s;
1979 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1980 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1982 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1988 // current_search_time() returns the number of milliseconds which have passed
1989 // since the beginning of the current search.
1991 int current_search_time() {
1993 return get_system_time() - SearchStartTime;
1997 // nps() computes the current nodes/second count
1999 int nps(const Position& pos) {
2001 int t = current_search_time();
2002 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
2006 // poll() performs two different functions: It polls for user input, and it
2007 // looks at the time consumed so far and decides if it's time to abort the
2010 void poll(const Position& pos) {
2012 static int lastInfoTime;
2013 int t = current_search_time();
2016 if (data_available())
2018 // We are line oriented, don't read single chars
2019 std::string command;
2021 if (!std::getline(std::cin, command))
2024 if (command == "quit")
2026 // Quit the program as soon as possible
2028 QuitRequest = StopRequest = true;
2031 else if (command == "stop")
2033 // Stop calculating as soon as possible, but still send the "bestmove"
2034 // and possibly the "ponder" token when finishing the search.
2038 else if (command == "ponderhit")
2040 // The opponent has played the expected move. GUI sends "ponderhit" if
2041 // we were told to ponder on the same move the opponent has played. We
2042 // should continue searching but switching from pondering to normal search.
2045 if (StopOnPonderhit)
2050 // Print search information
2054 else if (lastInfoTime > t)
2055 // HACK: Must be a new search where we searched less than
2056 // NodesBetweenPolls nodes during the first second of search.
2059 else if (t - lastInfoTime >= 1000)
2066 if (dbg_show_hit_rate)
2067 dbg_print_hit_rate();
2069 // Send info on searched nodes as soon as we return to root
2070 SendSearchedNodes = true;
2073 // Should we stop the search?
2077 bool stillAtFirstMove = FirstRootMove
2078 && !AspirationFailLow
2079 && t > TimeMgr.available_time();
2081 bool noMoreTime = t > TimeMgr.maximum_time()
2082 || stillAtFirstMove;
2084 if ( (UseTimeManagement && noMoreTime)
2085 || (ExactMaxTime && t >= ExactMaxTime)
2086 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2091 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2092 // while the program is pondering. The point is to work around a wrinkle in
2093 // the UCI protocol: When pondering, the engine is not allowed to give a
2094 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2095 // We simply wait here until one of these commands is sent, and return,
2096 // after which the bestmove and pondermove will be printed.
2098 void wait_for_stop_or_ponderhit() {
2100 std::string command;
2104 // Wait for a command from stdin
2105 if (!std::getline(std::cin, command))
2108 if (command == "quit")
2113 else if (command == "ponderhit" || command == "stop")
2119 // init_thread() is the function which is called when a new thread is
2120 // launched. It simply calls the idle_loop() function with the supplied
2121 // threadID. There are two versions of this function; one for POSIX
2122 // threads and one for Windows threads.
2124 #if !defined(_MSC_VER)
2126 void* init_thread(void* threadID) {
2128 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2134 DWORD WINAPI init_thread(LPVOID threadID) {
2136 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2143 /// The ThreadsManager class
2146 // read_uci_options() updates number of active threads and other internal
2147 // parameters according to the UCI options values. It is called before
2148 // to start a new search.
2150 void ThreadsManager::read_uci_options() {
2152 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2153 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2154 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2155 activeThreads = Options["Threads"].value<int>();
2159 // idle_loop() is where the threads are parked when they have no work to do.
2160 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2161 // object for which the current thread is the master.
2163 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2165 assert(threadID >= 0 && threadID < MAX_THREADS);
2168 bool allFinished = false;
2172 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2173 // master should exit as last one.
2174 if (allThreadsShouldExit)
2177 threads[threadID].state = THREAD_TERMINATED;
2181 // If we are not thinking, wait for a condition to be signaled
2182 // instead of wasting CPU time polling for work.
2183 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2184 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2186 assert(!sp || useSleepingThreads);
2187 assert(threadID != 0 || useSleepingThreads);
2189 if (threads[threadID].state == THREAD_INITIALIZING)
2190 threads[threadID].state = THREAD_AVAILABLE;
2192 // Grab the lock to avoid races with wake_sleeping_thread()
2193 lock_grab(&sleepLock[threadID]);
2195 // If we are master and all slaves have finished do not go to sleep
2196 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2197 allFinished = (i == activeThreads);
2199 if (allFinished || allThreadsShouldExit)
2201 lock_release(&sleepLock[threadID]);
2205 // Do sleep here after retesting sleep conditions
2206 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2207 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2209 lock_release(&sleepLock[threadID]);
2212 // If this thread has been assigned work, launch a search
2213 if (threads[threadID].state == THREAD_WORKISWAITING)
2215 assert(!allThreadsShouldExit);
2217 threads[threadID].state = THREAD_SEARCHING;
2219 // Here we call search() with SplitPoint template parameter set to true
2220 SplitPoint* tsp = threads[threadID].splitPoint;
2221 Position pos(*tsp->pos, threadID);
2222 SearchStack* ss = tsp->sstack[threadID] + 1;
2226 search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2228 search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2230 assert(threads[threadID].state == THREAD_SEARCHING);
2232 threads[threadID].state = THREAD_AVAILABLE;
2234 // Wake up master thread so to allow it to return from the idle loop in
2235 // case we are the last slave of the split point.
2236 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2237 wake_sleeping_thread(tsp->master);
2240 // If this thread is the master of a split point and all slaves have
2241 // finished their work at this split point, return from the idle loop.
2242 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2243 allFinished = (i == activeThreads);
2247 // Because sp->slaves[] is reset under lock protection,
2248 // be sure sp->lock has been released before to return.
2249 lock_grab(&(sp->lock));
2250 lock_release(&(sp->lock));
2252 // In helpful master concept a master can help only a sub-tree, and
2253 // because here is all finished is not possible master is booked.
2254 assert(threads[threadID].state == THREAD_AVAILABLE);
2256 threads[threadID].state = THREAD_SEARCHING;
2263 // init_threads() is called during startup. It launches all helper threads,
2264 // and initializes the split point stack and the global locks and condition
2267 void ThreadsManager::init_threads() {
2269 int i, arg[MAX_THREADS];
2272 // Initialize global locks
2275 for (i = 0; i < MAX_THREADS; i++)
2277 lock_init(&sleepLock[i]);
2278 cond_init(&sleepCond[i]);
2281 // Initialize splitPoints[] locks
2282 for (i = 0; i < MAX_THREADS; i++)
2283 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2284 lock_init(&(threads[i].splitPoints[j].lock));
2286 // Will be set just before program exits to properly end the threads
2287 allThreadsShouldExit = false;
2289 // Threads will be put all threads to sleep as soon as created
2292 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2293 threads[0].state = THREAD_SEARCHING;
2294 for (i = 1; i < MAX_THREADS; i++)
2295 threads[i].state = THREAD_INITIALIZING;
2297 // Launch the helper threads
2298 for (i = 1; i < MAX_THREADS; i++)
2302 #if !defined(_MSC_VER)
2303 pthread_t pthread[1];
2304 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2305 pthread_detach(pthread[0]);
2307 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2311 cout << "Failed to create thread number " << i << endl;
2315 // Wait until the thread has finished launching and is gone to sleep
2316 while (threads[i].state == THREAD_INITIALIZING) {}
2321 // exit_threads() is called when the program exits. It makes all the
2322 // helper threads exit cleanly.
2324 void ThreadsManager::exit_threads() {
2326 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2328 // Wake up all the threads and waits for termination
2329 for (int i = 1; i < MAX_THREADS; i++)
2331 wake_sleeping_thread(i);
2332 while (threads[i].state != THREAD_TERMINATED) {}
2335 // Now we can safely destroy the locks
2336 for (int i = 0; i < MAX_THREADS; i++)
2337 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2338 lock_destroy(&(threads[i].splitPoints[j].lock));
2340 lock_destroy(&mpLock);
2342 // Now we can safely destroy the wait conditions
2343 for (int i = 0; i < MAX_THREADS; i++)
2345 lock_destroy(&sleepLock[i]);
2346 cond_destroy(&sleepCond[i]);
2351 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2352 // the thread's currently active split point, or in some ancestor of
2353 // the current split point.
2355 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2357 assert(threadID >= 0 && threadID < activeThreads);
2359 SplitPoint* sp = threads[threadID].splitPoint;
2361 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2366 // thread_is_available() checks whether the thread with threadID "slave" is
2367 // available to help the thread with threadID "master" at a split point. An
2368 // obvious requirement is that "slave" must be idle. With more than two
2369 // threads, this is not by itself sufficient: If "slave" is the master of
2370 // some active split point, it is only available as a slave to the other
2371 // threads which are busy searching the split point at the top of "slave"'s
2372 // split point stack (the "helpful master concept" in YBWC terminology).
2374 bool ThreadsManager::thread_is_available(int slave, int master) const {
2376 assert(slave >= 0 && slave < activeThreads);
2377 assert(master >= 0 && master < activeThreads);
2378 assert(activeThreads > 1);
2380 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2383 // Make a local copy to be sure doesn't change under our feet
2384 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2386 // No active split points means that the thread is available as
2387 // a slave for any other thread.
2388 if (localActiveSplitPoints == 0 || activeThreads == 2)
2391 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2392 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2393 // could have been set to 0 by another thread leading to an out of bound access.
2394 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2401 // available_thread_exists() tries to find an idle thread which is available as
2402 // a slave for the thread with threadID "master".
2404 bool ThreadsManager::available_thread_exists(int master) const {
2406 assert(master >= 0 && master < activeThreads);
2407 assert(activeThreads > 1);
2409 for (int i = 0; i < activeThreads; i++)
2410 if (thread_is_available(i, master))
2417 // split() does the actual work of distributing the work at a node between
2418 // several available threads. If it does not succeed in splitting the
2419 // node (because no idle threads are available, or because we have no unused
2420 // split point objects), the function immediately returns. If splitting is
2421 // possible, a SplitPoint object is initialized with all the data that must be
2422 // copied to the helper threads and we tell our helper threads that they have
2423 // been assigned work. This will cause them to instantly leave their idle loops and
2424 // call search().When all threads have returned from search() then split() returns.
2426 template <bool Fake>
2427 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2428 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2429 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2430 assert(pos.is_ok());
2431 assert(ply > 0 && ply < PLY_MAX);
2432 assert(*bestValue >= -VALUE_INFINITE);
2433 assert(*bestValue <= *alpha);
2434 assert(*alpha < beta);
2435 assert(beta <= VALUE_INFINITE);
2436 assert(depth > DEPTH_ZERO);
2437 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2438 assert(activeThreads > 1);
2440 int i, master = pos.thread();
2441 Thread& masterThread = threads[master];
2445 // If no other thread is available to help us, or if we have too many
2446 // active split points, don't split.
2447 if ( !available_thread_exists(master)
2448 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2450 lock_release(&mpLock);
2454 // Pick the next available split point object from the split point stack
2455 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2457 // Initialize the split point object
2458 splitPoint.parent = masterThread.splitPoint;
2459 splitPoint.master = master;
2460 splitPoint.betaCutoff = false;
2461 splitPoint.ply = ply;
2462 splitPoint.depth = depth;
2463 splitPoint.threatMove = threatMove;
2464 splitPoint.mateThreat = mateThreat;
2465 splitPoint.alpha = *alpha;
2466 splitPoint.beta = beta;
2467 splitPoint.pvNode = pvNode;
2468 splitPoint.bestValue = *bestValue;
2470 splitPoint.moveCount = moveCount;
2471 splitPoint.pos = &pos;
2472 splitPoint.nodes = 0;
2473 splitPoint.parentSstack = ss;
2474 for (i = 0; i < activeThreads; i++)
2475 splitPoint.slaves[i] = 0;
2477 masterThread.splitPoint = &splitPoint;
2479 // If we are here it means we are not available
2480 assert(masterThread.state != THREAD_AVAILABLE);
2482 int workersCnt = 1; // At least the master is included
2484 // Allocate available threads setting state to THREAD_BOOKED
2485 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2486 if (thread_is_available(i, master))
2488 threads[i].state = THREAD_BOOKED;
2489 threads[i].splitPoint = &splitPoint;
2490 splitPoint.slaves[i] = 1;
2494 assert(Fake || workersCnt > 1);
2496 // We can release the lock because slave threads are already booked and master is not available
2497 lock_release(&mpLock);
2499 // Tell the threads that they have work to do. This will make them leave
2500 // their idle loop. But before copy search stack tail for each thread.
2501 for (i = 0; i < activeThreads; i++)
2502 if (i == master || splitPoint.slaves[i])
2504 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2506 assert(i == master || threads[i].state == THREAD_BOOKED);
2508 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2510 if (useSleepingThreads && i != master)
2511 wake_sleeping_thread(i);
2514 // Everything is set up. The master thread enters the idle loop, from
2515 // which it will instantly launch a search, because its state is
2516 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2517 // idle loop, which means that the main thread will return from the idle
2518 // loop when all threads have finished their work at this split point.
2519 idle_loop(master, &splitPoint);
2521 // We have returned from the idle loop, which means that all threads are
2522 // finished. Update alpha and bestValue, and return.
2525 *alpha = splitPoint.alpha;
2526 *bestValue = splitPoint.bestValue;
2527 masterThread.activeSplitPoints--;
2528 masterThread.splitPoint = splitPoint.parent;
2529 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2531 lock_release(&mpLock);
2535 // wake_sleeping_thread() wakes up the thread with the given threadID
2536 // when it is time to start a new search.
2538 void ThreadsManager::wake_sleeping_thread(int threadID) {
2540 lock_grab(&sleepLock[threadID]);
2541 cond_signal(&sleepCond[threadID]);
2542 lock_release(&sleepLock[threadID]);
2546 /// RootMove and RootMoveList method's definitions
2548 RootMove::RootMove() {
2551 pv_score = non_pv_score = -VALUE_INFINITE;
2555 RootMove& RootMove::operator=(const RootMove& rm) {
2557 const Move* src = rm.pv;
2560 // Avoid a costly full rm.pv[] copy
2561 do *dst++ = *src; while (*src++ != MOVE_NONE);
2564 pv_score = rm.pv_score;
2565 non_pv_score = rm.non_pv_score;
2569 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2570 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2571 // allow to always have a ponder move even when we fail high at root and also a
2572 // long PV to print that is important for position analysis.
2574 void RootMove::extract_pv_from_tt(Position& pos) {
2576 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2580 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2582 pos.do_move(pv[0], *st++);
2584 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2585 && tte->move() != MOVE_NONE
2586 && move_is_legal(pos, tte->move())
2588 && (!pos.is_draw() || ply < 2))
2590 pv[ply] = tte->move();
2591 pos.do_move(pv[ply++], *st++);
2593 pv[ply] = MOVE_NONE;
2595 do pos.undo_move(pv[--ply]); while (ply);
2598 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2599 // the PV back into the TT. This makes sure the old PV moves are searched
2600 // first, even if the old TT entries have been overwritten.
2602 void RootMove::insert_pv_in_tt(Position& pos) {
2604 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2607 Value v, m = VALUE_NONE;
2610 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2614 tte = TT.retrieve(k);
2616 // Don't overwrite exsisting correct entries
2617 if (!tte || tte->move() != pv[ply])
2619 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2620 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2622 pos.do_move(pv[ply], *st++);
2624 } while (pv[++ply] != MOVE_NONE);
2626 do pos.undo_move(pv[--ply]); while (ply);
2629 // pv_info_to_uci() returns a string with information on the current PV line
2630 // formatted according to UCI specification and eventually writes the info
2631 // to a log file. It is called at each iteration or after a new pv is found.
2633 std::string RootMove::pv_info_to_uci(const Position& pos, Value alpha, Value beta, int pvLine) {
2635 std::stringstream s, l;
2638 while (*m != MOVE_NONE)
2641 s << "info depth " << Iteration // FIXME
2642 << " seldepth " << int(m - pv)
2643 << " multipv " << pvLine + 1
2644 << " score " << value_to_uci(pv_score)
2645 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2646 << " time " << current_search_time()
2647 << " nodes " << pos.nodes_searched()
2648 << " nps " << nps(pos)
2649 << " pv " << l.str();
2651 if (UseLogFile && pvLine == 0)
2653 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2654 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2656 LogFile << pretty_pv(pos, current_search_time(), Iteration, pv_score, t, pv) << endl;
2662 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
2664 SearchStack ss[PLY_MAX_PLUS_2];
2665 MoveStack mlist[MOVES_MAX];
2669 // Initialize search stack
2670 init_ss_array(ss, PLY_MAX_PLUS_2);
2671 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2673 // Generate all legal moves
2674 MoveStack* last = generate_moves(pos, mlist);
2676 // Add each move to the RootMoveList's vector
2677 for (MoveStack* cur = mlist; cur != last; cur++)
2679 // If we have a searchMoves[] list then verify cur->move
2680 // is in the list before to add it.
2681 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2683 if (searchMoves[0] && *sm != cur->move)
2686 // Find a quick score for the move and add to the list
2687 pos.do_move(cur->move, st);
2690 rm.pv[0] = ss[0].currentMove = cur->move;
2691 rm.pv[1] = MOVE_NONE;
2692 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2695 pos.undo_move(cur->move);
2700 // Score root moves using the standard way used in main search, the moves
2701 // are scored according to the order in which are returned by MovePicker.
2702 // This is the second order score that is used to compare the moves when
2703 // the first order pv scores of both moves are equal.
2705 void RootMoveList::set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss)
2708 Value score = VALUE_ZERO;
2709 MovePicker mp(pos, ttm, ONE_PLY, H, ss);
2711 while ((move = mp.get_next_move()) != MOVE_NONE)
2712 for (Base::iterator it = begin(); it != end(); ++it)
2713 if (it->pv[0] == move)
2715 it->non_pv_score = score--;
2720 // Overload operator << to make it easier to print moves in coordinate notation
2721 // (g1f3, a7a8q, etc.). The only special case is castling moves, where we
2722 // print in the e1g1 notation in normal chess mode, and in e1h1 notation in
2725 std::ostream& operator<<(std::ostream& os, Move m) {
2727 Square from = move_from(m);
2728 Square to = move_to(m);
2729 bool chess960 = (os.iword(0) != 0); // See set960()
2732 return os << "(none)";
2735 return os << "0000";
2737 if (move_is_short_castle(m) && !chess960)
2738 return os << (from == SQ_E1 ? "e1g1" : "e8g8");
2740 if (move_is_long_castle(m) && !chess960)
2741 return os << (from == SQ_E1 ? "e1c1" : "e8c8");
2743 os << square_to_string(from) << square_to_string(to);
2745 if (move_is_promotion(m))
2746 os << char(tolower(piece_type_to_char(move_promotion_piece(m))));